Adequate cardiac output is necessary in order to supply oxygen and other nutrients to all body tissues. Cardiac output is influenced by stroke volume and heart rate. Factors affecting the stroke volume include PRELOAD, CONTRACTILITY, and AFTERLOAD.
In the following conditions, indicate what factor/s influence the cardiac output: PRELOAD, CONTRACTILITY, AFTERLOAD, HEART RATE. Explain why the factor/s affects cardiac output in 1 to 2 sentences.
a. High blood pressure
Any increases in cardiac output (HR and/or SV), blood viscosity, or total peripheral resistance will result in increases in BP. Some of these factors include sympathetic stimulation, the catecholamines epinephrine and norepinephrine, thyroid hormones, and increased calcium ion levels.
b. Massive bleeding
The reduction in blood volume during acute blood loss causes a fall in central venous pressure and cardiac filling, both leading to reduced cardiac output and arterial pressure.
c. the drug dopamine
Dopamine increases heart rate and cardiac contractility through having beneficial chronotropic and inotropic effects on the myocardium. It is applied in a clinical setting to support blood pressure, cardiac output, and diuresis.
d. Running a sprint
Due to the relatively high heart rates that are reached during exercise, cardiac output increases significantly when one runs a sprint. As both heart rate and stroke volume increase, so does the cardiac output.
e. Hyperthyroidism with increased secretion of thyroid hormones
Hyperthyroidism's hemodynamic changes reduce myocardial contractile reserve, preventing further increases in cardiac output and ejection fraction during exercise. Excess thyroid hormone alters hemodynamics, which puts the patient at risk for heart failure.
f. Massive myocardial infarction (cardiac tissue death)
A massive myocardial infarction impairs global cardiac function, which can lead to reduced cardiac output. Systolic and diastolic dysfunction are associated with ischemic myocardium due to decreased coronary perfusion leads to muscle hypoxia and necrosis which compromises myocardial contractility.
g. Hypothermia
There is a reflex adrenergic vasoconstriction (noradrenalin) of the skin with a decrease in core temperature (hypothermia). Increased bradycardia, which lowers stroke volume, causes cardiac output to drop below a core temperature of 34 degrees Celsius.
h. Emotional distress
Emotional distress can elicit increased cardiac output, increased systemic vascular resistance, and thus an elevation of arterial blood pressure. Your heart may beat more quickly as a result of the aforementioned phenomena, and your blood vessels may constrict to help push blood to the body's center.
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References:
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